The present invention concerns an audio amplifier switch-on control circuit.
It is known that in audio, TV and radio equipment, interference can be produced, upon switching on, at the audio amplifier outlet, that is in the loudspeaker, due to settling defects in the upstream circuits. Such disturbances are commonly called "switch-on noise".
This inconvenience can be overcome by using a so-called "muting" circuit, which controls the switch-on time of the audio amplifier so as to make it become dynamic only after the circuits upstream have duly settled. In other words, the audio amplifier is "muted", and the input audio signal is prevented from reaching the loudspeaker, as long as the circuits upstream remain in a condition such as to generate switch-on noise.
It is also known that in such equipment a "stand-by" function is sometimes provided, in which the equipment is held in a waiting condition with minimum absorption, which allows subsequent turning on again of the power part by nonpower telecontrol or switch. Switching on again after "stand-by" must naturally take place without noise production, that is with an appropriate delay in audio amplifier switch-on time.
The primary object of the present invention is to accomplish an audio amplifier control circuit capable of appropriately delaying the audio amplifier switch-on time upon each new switching on of the equipment, however controlled.
Another object of the present invention is to accomplish an audio amplifier control circuit also capable of causing switching off, and then correct switching on again, of the audio amplifier after a "stand-by" command.